The present invention relates to test apparatus for determining erosion and, in particular, to apparatus for spinning a specimen in an abrasive medium.
To facilitate preventative maintenance, it is useful to estimate in advance the annual wear that can be expected within a vessel, pipe or other device. For example, a vessel or pipe fabricated from a special alloy and/or lined with a ceramic coating or other castable refractory material may be subjected to a service environment wherein high speed particles impinge against the interior of the pipe or vessel at glancing angles. Furthermore, these particles may be at a fairly high (or low) temperature and be propelled by a corrosive gaseous ambient. The particles can constitute any material or mixture of materials including coal, catalyst, sand, shale, sulphur silicon carbide, or other abrasive material. These particles can typically range in size between 10 to 1000 .mu.m at speeds between 0.01 to 400 feet per second, although other speeds and sizes are possible.
A known erosion resistance test is disclosed in ASTM 704-76A, entitled "Standard Method for Abrasion Resistance of Refractory Material at Room Temperature." In the test, size graded silicon carbide is blasted by air pressure normally against a flat specimen. The extent of erosion over a predetermined interval is used as a measure of the erosion resistance of the specimen. However, this high angle of incidence at a high velocity is often unrepresentative of the conditions under whih a specimen is actually used. Such a test takes into account neither the actual, small, glancing angles of the particles nor the actual temperatures, nor the effect of a corrosive gaseous ambient. Furthermore, an unrepresentatively high-velocity, normal collision by a particle may cause unrepresentative microfracture of a brittle non-metallic target such as glass, refractories, bricks etc.
In a known test method (for example, expired U.S. Pat. No. 1,961,333) a disc is rotated in a hopper containing sand or finely divided carborundum. This disc is rotated for a predetermined length of time while the revolutions are counted, in order to measure the wearing qualities of a surface finish. However, this apparatus is not useful for simulating a specific environment. Furthermore, this known apparatus does not employ a variable speed motor for rotating a disc at a speed which simulates the speed of particles impinging on the disc under a specific service environment. Also, this known apparatus is not useful for testing the disc with a hot abrasive medium since its hopper is neither insulated nor are the bearings protected against high temperatures.
Accordingly, there is a need for a rapid, simple, and effective erosion test that simulates the erosion occurring under actual service conditions.